A printer which prints desired character or image information on a sheet type print medium such as paper or a film is known as an information output apparatus in a word processor, a personal computer, a facsimile machine and the like.
In recent years, among various known printing methods, an inkjet method especially attracts attention in recent years by virtue of its capabilities of printing without contact with a print medium such as a print sheet and color printing, a low running cost, quiet operation by non-impact method and the like.
Further, among the inkjet printing apparatuses, a full-line type printing apparatus having a printhead with a printing element (nozzle) array corresponding to a printing width, which performs printing while conveying a print medium, is becoming widely used since the printing speed can be further increased.
In this full-line type printing apparatus, plural printheads to discharge different color inks are arrayed in a conveying direction of the print medium, and the inks are simultaneously discharged from the respective printheads, thereby the printing speed is not lowered even upon color printing.
In this printing apparatus, when all the printheads are simultaneously driven, electric power necessary for the printing exceeds the power supply capability of a power source. Accordingly, in many cases, when power necessary for printing, calculated from the number of driven printing elements or the like exceeds a predetermined threshold value, the electric consumption is reduced by e.g. changing a printhead driving frequency.
In this inkjet printing apparatus, the printhead is schematically constructed with an energy generator to generate energy to be supplied to ink, for discharging the ink from a discharge orifice as ink droplets, an ink channel including the energy generator inside and communicated with the discharge orifice, and ink containing means such as an ink tank containing the ink supplied through the ink channel to the energy generator.
In the printhead, to maintain an excellent ink discharge state in each printing element, preliminary discharge to discharge ink from the orifices of the respective printing elements must be performed periodically.
For this purpose, the printing apparatus has containing means for containing preliminarily-discharged ink, suction means for moving the ink stored in the containing means to a predetermined position, and the like. Further, the containing means has cap means for moisture retention of the discharge orifices of the respective printing elements, thus constructs, with the suction means, recovery means for recovery of the discharge characteristic of the printhead.
Upon printing on plural print media, to maintain printing quality and discharge performance, it is necessary to perform recovery processing or preliminary discharge in the middle of the printing. However, if the recovery processing using the recovery means is performed in the middle of the printing operation, as the printing is suspended, the printing time is greatly prolonged.
For this reason, to maintain the discharge performance without increasing the printing time, the preliminary discharge is performed, in place of the recovery processing, on a print medium or on a conveying member to convey the print medium.
Accordingly, in the full-line type printing apparatus having plural printheads, printing on a print medium and the preliminary discharge are simultaneously performed. As the above-described predetermined threshold value regarding the electric power is set to a maximum value that the power source can supply, if electric power by the preliminary discharge is added, the electric consumption may exceed the capability of the power source.